The common reasons for newborns to urinate less than three days are improper feeding, environmental discomfort, and pathological reasons cannot be ruled out, such as gastrointestinal infections. 1. Improper feeding: some new mothers postpartum nervousness or overwork resulting in insufficient milk, late milk, newborns therefore intake of milk is insufficient, resulting in less urine, some newborns drink milk with the nipple is easy to fall asleep, resulting in each time into the amount of milk is less, the amount of urine will naturally be reduced. 2. environmental discomfort: if the newborn wear a lot, covered with very hot, the newborn itself metabolism is vigorous, easy to sweat, there will be water loss phenomenon, if there is no timely rehydration, the baby’s urine decreased. 3. Pathological reasons: the newborn immune system has not yet developed, such as gastrointestinal infections may cause increased sweating, diarrhea, etc., resulting in dehydration, thus leading to oliguria. There are many reasons why a newborn’s urine output decreases, and it may also be caused by kidney disease. It is recommended to bring your newborn to the hospital to find out the cause of the problem and give him/her the appropriate treatment if his/her urine output does not decrease.